<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
  <h1>The Ajax 02 Page</h1>
  <button onclick="doAjaxGet()">Do Ajax Get</button>
  <button onclick="doAjaxPost()">Do Ajax Post</button>
  <button onclick="doAjaxDelete()">Do Ajax Delete</button>
  <button onclick="doAjaxUpdate()">Do Ajax Update</button>
  <div id="result"></div>
  <script>
      //发送ajax get请求,将服务端doAjaxGet函数的响应结果更新到result位置
      function doAjaxGet(){
         let xhr=new XMLHttpRequest();
         xhr.onreadystatechange=function(){
             if(xhr.readyState==4){
                 if(xhr.status==200){
                    document.getElementById("result").innerHTML=xhr.responseText;
                 }
             }
         }
         xhr.open("GET","http://localhost/doAjaxGet",true);
         xhr.send(null);
      }
      function doAjaxPost(){
          let xhr=new XMLHttpRequest();
          xhr.onreadystatechange=function(){
              if(xhr.readyState==4){
                  if(xhr.status==200){
                      document.getElementById("result").innerHTML=xhr.responseText;
                  }
              }
          }
          xhr.open("POST","http://localhost/doAjaxPost",true);
          //post请求向服务端传递数据,需要设置请求头,必须在open之后
          xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
          //发送请求(post请求传递数据,需要将数据写入到send方法内部)
          xhr.send("id=101&name=Computer&remark=Computer...");
      }

      function doAjaxDelete(){
          let xhr=new XMLHttpRequest();
          xhr.onreadystatechange=function(){
              if(xhr.readyState==4){
                  if(xhr.status==200){
                      document.getElementById("result").innerHTML=xhr.responseText;
                  }
              }
          }
          xhr.open("delete","http://localhost/doAjaxDelete?id=101",true);
          xhr.send(null);
      }

      function doAjaxUpdate(){
          let xhr=new XMLHttpRequest();
          xhr.onreadystatechange=function(){
              if(xhr.readyState==4){
                  if(xhr.status==200){
                      document.getElementById("result").innerHTML=xhr.responseText;
                  }
              }
          }
          xhr.open("put","http://localhost/doAjaxUpdate",true);
          //post请求向服务端传递数据,需要设置请求头,必须在open之后
          xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
          //发送请求(post请求传递数据,需要将数据写入到send方法内部)
          xhr.send("id=101&name=Book&remark=Book...");
      }

  </script>

</body>
</html>